Strong sell bias stays with insiders as market hits highs

A strong sell bias continues among company insiders across the market, as stocks breach trough historic levels.

The S&P 500 is up 26 percent year-to-date, tracking for its best yearly gain in a decade. Other market indexes such as the Nasdaq, Russell 2000 and Dow transportation average are up more than 32 percent this year, respectively. The S&P, Dow, Russell and transports are trading at or near record highs, while the Nasdaq crossed the 4,000 mark for the first time in 13 years.

As the market continues to gain steam, corporate insiders are unwinding their positions at a similar rate. Research firm InsiderScore highlights that the sentiment being displayed is not surprising given the market backdrop along with tax season approaching, but emphasizes that investors should not lose sight of the trend and continue to drill down on individual companies.

The technology and industrial goods sectors remain the main drivers of negative sentiment while the energy and health-care sectors are showing the most positive sentiment, according to InsiderScore. There's also been an increase in "cluster sales" across a number of sectors—cluster sales occur when at least three officers unwind their positions.

In November alone, corporate insiders of S&P 500 companies sold about $7.4 billion worth of stock, an 85 percent increase from October and the highest amount since May, which is the peak so far this year, according to FactSet.

Below is a look at some of the names with the biggest insider sells and purchases in the past three months.